A Cartesian cut cell method for axisymmetric separating body flows

Numerical simulations of unsteady, axisymmetric compressible flows involving both fixed and separating bodies are presented. The method uses a Cartesian cut cell mesh approach and a high resolution, upwind finite volume scheme. Firstly, a stationary background Cartesian mesh is generated on the computational domain, and complex solid geometries are represented by different types of cut cell. Secondly, the solid bodies are allowed to move across the mesh and a modified finite volume algorithm is used to deal with moving boundary problems. The flow solver employed is a MUSCL-Hancock, Godunov-type scheme in conjunction with an HLLC approximate Riemann solver (for flow interfaces) and an exact Riemann solver for a moving piston (for fixed or moving solid faces). A cell merging technique is used to maintain numerical stability in the presence of arbitrarily small cut cells and to retain strict conservation on moving boundaries. The method is applied to muzzle blast flow and muzzle break problems involving both fixed and separating bodies.